Chapter 7 Electrochemistry 87.9 Electrode potential and electromotive forces
Chapter 7 Electrochemistry §7.9 Electrode potential and electromotive forces
Our Goals (1) Calculate unknown potential from given potentials (2)explain the principle for potentiometric analysis ()Construct and apply simple pourbaix diagram
Our Goals (1) Calculate unknown potential from given potentials (2) explain the principle for potentiometric analysis; (3) Construct and apply simple Pourbaix diagram
87.9 Electrode potential and electromotive forces 7.9.3 Relationship between different electrode potentials between different oxidation states Give the relationship between F 2+ Fe Initial state and final state
between different oxidation states Give the relationship between Initial state and final state 7.9.3 Relationship between different electrode potentials §7.9 Electrode potential and electromotive forces
87.9 Electrode potential and electromotive forces 7.9.4 Relationship between different electrode potentials p of relevant electrodes AgCl=Ag cl- rIIna rt k ( Ag(s)AgNO3(c,)llKCI(c2)AgCI(slAg(s) D .IA ne nkp nAcl RT RT 1 e=AgCVAg E Ag /Ag AgCl+ le=Ag+CI- RT n nF RT aAgCI RT 9 AgCl/Ag Exercise: deduce the relationship between Ag(CN)/Ag and Ag/Ag
AgCl = Ag+ + ClAg(s)|AgNO3 (c1 ) ||KCl(c2 ) |AgCl(s)|Ag(s) of relevant electrodes Ag /Ag + AgCl/Ag AgCl/Ag + Ag /Ag E = − sp ln RT E K nF = - Ag(CN) /Ag 2 + Ag /Ag Exercise: deduce the relationship between and 7.9.4 Relationship between different electrode potentials + + + Ag /Ag Ag Ag /Ag Cl Ag /Ag Cl ln ln 1 ln ln sp sp RT RT k a nF nF a RT RT k nF nF a + − − = + = + = + + AgCl + 1e - = Ag + ClAgCl AgCl/Ag AgCl/Ag Ag Cl Cl 1 ln ln RT RT a nF a a nF a − − = + = + §7.9 Electrode potential and electromotive forces
87.9 Electrode potential and electromotive forces 7.9.5 Concentration-dependence of Nernst equation 0=pR7 H, nF for Agt/Ag electrode Pt electrode o RT g/As g nF P(Ag/Ag)depends on [ag], or (Ag/Ag Can we use hydrogen electrode for responds to [Ag]. The relationship between measuring the ph of the solution? P(*/Ag) and [Ag can be used for Give the principle of the measurement. quantitative electroanalysis of Ag
7.9.5 Concentration-dependence of Nernst equation ox red ln RT a nF a = + for Ag+ /Ag electrode + + Ag /Ag Ag /Ag Ag ln RT a nF = + + (Ag+ /Ag) depends on [Ag+ ] , or (Ag+ /Ag) responds to [Ag+ ]. The relationship between (Ag+ /Ag) and [Ag+ ] can be used for quantitative electroanalysis of Ag+ . Can we use hydrogen electrode for measuring the pH of the solution? Give the principle of the measurement. §7.9 Electrode potential and electromotive forces
87.9 Electrode potential and electromotive forces 7.9.6 pH-dependence of Pourbaix diagram For electrode reaction with Ht or OH participating in, the electrode potential will depend on ph. 1.229 2H+2e—>H2 q=ge+0.05916la 0,401 =0.000-0.05916pH 0.000 H2 O,+4H++4e-)2H,o -0.828 q=p+0.05916lga =12290.05916pH 02468101214pH pH-potential diagram/Pourbaix diagram
7.9.6 pH-dependence of : Pourbaix diagram For electrode reaction with H+ or OH- participating in, the electrode potential will depend on pH. O2 + 4H+ + 4e - ⎯→ 2H2O = ⊖ + 0.05916 lgaH + = 1.229 - 0.05916 pH = ⊖ + 0.05916 lgaH + = 0.000 - 0.05916 pH 2H+ + 2e- ⎯→ H2 pH-potential diagram/Pourbaix diagram §7.9 Electrode potential and electromotive forces
87.9 Electrode potential and electromotive forces 7.9.4 pH-dependence of Pourbaix diagram ATLAS o ELECTROCHEMICAL LQUILIaEIA s84104s090H09 2.0 1.6 Feo 1.2 0.8 >0.4 Fe O.nH,O Marcel Pourbaix (1904-1998) s a Russian-born belgian chemist -0.4 Pourbaix(left)and Evans(right) -0.8 Fe 图形化方法( Graphic method, visualization) 14
Pourbaix (left) and Evans (right) 图形化方法（Graphic method, visualization） 7.9.4 pH-dependence of : Pourbaix diagram Marcel Pourbaix (1904–1998), a Russian-born, Belgian chemist. §7.9 Electrode potential and electromotive forces
87.9 Electrode potential and electromotive forces .9.4 pH-dependence of Pourbaix diagram Construction of Pourbaix diagram (1) When we plate Cu, why do we use acidic copper sulfate solution? (2)When we anodize copper in neural solution Cu Cu(oH)2 what phenomenon can we observed? Cuo Cuo Cu 02468101214
Construction of Pourbaix diagram Cu2+ Cu(OH)2 Cu pH / V 0 2 4 6 8 10 12 14 CuO2 2− Cu2O 7.9.4 pH-dependence of : Pourbaix diagram (1) When we plate Cu, why do we use acidic copper sulfate solution? (2) When we anodize copper in neural solution, what phenomenon can we observed? §7.9 Electrode potential and electromotive forces